Read/write head structures colloquially known as “sliders” typically are manufactured in groups on a semiconductor wafer. To track individual sliders, heretofore indicia representing each slider's position on the wafer have been optically formed on the “front” of the wafer next to each slider, while a serial number representing the wafer has been formed by laser projection or etching on the “back” surface of the slider. Such tracking a necessary for, e.g., process control, to ascertain for instance whether sliders at a particular wafer position wafer-to-wafer are being defectively made, or whether a particular wafer or series of wafers produce defective sliders.
As critically recognized herein, present processing of slider wafers can require lapping the wafers to be even thinner than they are when they are originally received from the wafer supplier with the wafer serial numbers on the back surfaces. This can entail lapping the back surface in a way that erases the serial numbers. Moreover, the present invention recognizes that forming serial numbers using projection technology such as lasers can produce contaminants during the ablating process, leading to eventual slider failures. Still further, the present invention critically recognizes that with ever-shrinking slider dimensions, the resolution and placement afforded by laser technology grows ever more insufficient. Additionally, with respect to etching, a small etch cavity may remain after etching, and the cavity may trap debris, contaminating the device. With these critical recognitions in mind, the present invention is provided.